I tracked down my coolant leak to the water pump. In removing the pump I can see it is leaking past the bearing and the impeller has seen better days. The new water pump part has turned up (636 200 16 01) and I need to move the pulley from the failed unit across.

Looking at the 170 workshop manual (M45A, page 59) there are two steps to remove the pulley - I do not have the Mercedes tools specified and it is not entirely clear how to go about it.

Step 1 looks like clamping the water pump and somehow removing the lock washer - I am not sure how I can access the lock washer that I assume is in the pulley shaft hole?Step 2 is using a puller to remove the pulley - I have seen generic power steering and similar pulley removal kits, would one of these work?